Method of preparing petroleum fractions of improved odor using beta-lactones



Uted States atent METHOD OF PREPARING PETROLEUM FRAC- TIONS OF IMPROVEDODOR USING fl-LAC- TONES George W. Ayers, Chicago, and William A;Krewer,

Arlington Heights, IlL, assignors to The Pure Oil Company, Chicago, IlL,a corporation of Ohio No Drawing. Filed May 3, 1961, Ser. No. 120,456

20 Claims. (Cl. 208199) This invention relates to the preparation ofpetroleum fractions of improved odor and, more particularly, to the useof fl-lactones in improving the odor of distillate furnace oils.

The presence of appreciable quantities of mercaptans in distillatefurnace oils, or components thereof, obtained from many crude oils, isundesirable due to their very objectionable odors. The odors of suchpetroleum fractions must be improved before they are suitable formarketing. The odors are improved either by removing the mercaptans fromthe oils or by converting them into substances having lowerodor-imparting characteristics. One of the well-known processes forconverting these objectional substances to less obnoxious compounds isdoctor treatment. In this sweetening process, the odorous petroleumfraction is treated withan aqueous solution of an alkali metal hydroxidecontaining sodium plumbite and elementary sulfur. The mercaptans areconverted into disulfides, which have much lower odorimpartingproperties, and the doctor-treated petroleum fraction exhibits a greatimprovement in odor. The amount of elementary sulfur used in doctortreatment is rigidly controlled so that barely enough sulfur is presentto obtain precipitation, or break, of lead sulfide from the petroleumfraction and conversion of mercaptans into disulfides. The settling ofthe dark-colored material from the petroleum fractions leaves a clearsweetened product of good odor. The principal disadvantages of thedoctor treatment are that the sulfur content of the product oil isessentially the same as that of the untreated oil, and that extreme caremust be exercised not to use excess sulfur or the product oil will becorrosive to metals such as copper and hence unsuitable for marketing.In addition, in the case of certain very odorous petroleum fractions,extreme difficulty is experienced in obtaining the break even when anundesirable excess of sulfur is present, and a long time interval may berequired.

In accordance with the present invention, it has been found that theodor of furnace oils is improved by treatment with a fl-lactone and analkali metal hydroxide. It has been found that in treating odoriferousfurnace oils with an aqueous alkali metal hydroxide solution and a,B-lactone, a portion of the obnoxious sulfur compounds which impartsodors to the oils is removed and there is a decrease in the total sulfurcontent of the treated oils. It has also been found that a preliminarytreatment of exceedingly odoriferous petroleum fractions with a plactoneand an aqueous alkali metal hydroxide solution significantly reduces thetime required for the doctor break, as well as the sulfur requirement,during a subsequent doctor treatment. As an alternative method ofapplication, the B-lactone may be added to the doctor solution. Othermethods of application will become ap parent from a further descriptionof this invention.

Accordingly, it is a primary object of this invention to provide aprocess of preparing a petroleum fraction of improved odor.

Another object of this invention is to provide a process for sweeteningfurnace oils.

Another object of this invention is to provide a reduction in the timeand elementary sulfur requirements for doctor-treating petroleumfractions.

ice

Another object of this invention is to provide a process for removingodoriferous materials from petroleum fractions by treatment with anaqueous alkali metal hydroxide solution and a {i-lactone.

These and further objects of the invention will become apparent as thespecification herein proceeds.

This invention is directed to the use of the combination of a fi-lactoneand caustic solution in removing odoriferous substances from certainpetroleum fractions. The B-lactones which are used have the reactivenucleus 0- :0 with the free valences preferably satisfied by hydrogen orhydrocarbon radicals such as alkyl, cycloalkyl, aryl or alkarylradicals. More specifically, it is preferred that the hydrocarbonradicals contain 1 to 10 carbon atoms. Non-limting examples of compoundscoming within the scope of the foregoing formula and definition are:

fl-Propiolactone fl-Butyrolactone fi-methyl-fi-propiolactone)B-Methyl-B-butyrolactone (B-p-dimethyl-fi-propiolactone)fl-Ethyl-fi-butyrolactone fl-Phenyl-B-propiolactone The fi-lactonereacts especially with tertiary mercaptans, such as aromatic mercaptansof the thiophenol type, in the presence of the alkali solution. Themercaptans are converted into water-soluble substances, thus loweringthe sulfur content of the petroleum fraction. The reaction proceeds asrepresented by the following equation:

our-on,

| A} ormsn mon o-- =0 fi-Propiolactone Phenylmer- Sodium captan(thiohydroxide phenol) 0 CuHs-S-OHrCHz-O H2O O-Nd- Sodiumphenylmercaptopropionate Water The B-lactones show a negligiblereactivity with the mercaptans unless a caustic solution is present. Thefi-lactone and caustic may be added to the petroleum fractionsimultaneously or separately. It is preferred that the t3- lactone notbe added to the caustic solution prior to the caustic solution beingadded to the petroleum fraction since the lactone will also react withit to give, with propiolactone for example, sodium hydracrylate. Thisreaction is less rapid than the reaction with the mercaptans. If the[i-propiolactone is added to the caustic solution for any appreciablelength of time prior to its use in treating the sour petroleum fraction,appreciable amounts of the fl-lactone will be lost in the reaction withthe caustic solution.

The amount of the ,B-lactone used per amount of petroleum fraction willdepend upon the amount of the reactive odoriferous mercaptans present inthe petroleum fraction to be treated. At least a st'oichiometric amountof the p-lactone to react with the active mercaptans present in thepetroleum fraction should be used. An excess over the stoichiornetricamount is recommended.

A temperature of about to 230 F. is preferred during the treatment ofthe oil with the B-lactone and aqueous caustic solution. Othertemperatures may be used, but temperatures lower than about 150 F. willrequire longer contact periods than are considered practical. A contacttime of about one to ten minutes is effective at temperatures of about150 to 230 F. The

method of contacting may be mechanical or by turbulent flow. The processof this invention may be conducted batchwise as well as continuously.

At least a stoichiometric amount of the caustic soda is added preferablyas a 1 to 25% aqueous solution, although other concentrations may beused. Although sodium hydroxide is preferred because of its cheapness,other alkali metal hydroxides, such as potassium hydroxide or lithiumhydroxide, or any combination of these three alkali metal hydroxides,may be used. The caustic solution may be used repeatedly, (1) withperiodic additions of fresh caustic, until the accumulation of saltsnecessitates discarding the solution, or (2) with continuous or periodicadditions of fresh caustic (or caustic solution) with continuous orperiodic withdrawals of equivalent volumes of the used caustic solution.

If the B-lact-one is added during the doctor treatment instead of beingused in a preliminary treatment with an aqueousalkali metal hydroxidsolution, not more than one mole of B-lactone should be used per mole ofmercaptan present in the oil to be treated. This is preferred to preventrapid fouling of the doctor solution with alkali metal salts which arenot removed by the usual methods of regeneration of the doctor solution.

The petroleum fractions that can be treated successfully in accordancewith this invention include those that contain tertiary mercaptans,particularly aromatic mercaptans of thiophenolic type and othermercaptans not of the primary or secondary types, as an appreciable partof their mercaptan content. Virgin and cracked petroleum fractionsboiling in the range of approximately 300 F. to 700 F. are especiallysusceptible to treatment in accordance with this invention. The presentinvention is also specially applicable to those petroleum fractions withwhich difiiculty is experienced in obtaining breakout of doctor sludgeduring doctor treating.

In order to demonstrate the invention, the following examples arepresented:

Example I A 100-gram sample of a poor-odor-quality furnace-oil stock(352550 F. boiling range), obtained from a mixture of western sour crudeoils and containing 0.05% mercaptan sulfur and 0.53% total sulfur, wastreated with grams of 20% sodium hydroxide solution and 3.6 grams offi-propiolactone at 230 F. for one hour with mechanical stirring. Afterthis treatment, the mixture was cooled to room temperature and the oiland aqueous phases were separated. Following this, the oil waswater-washed until the washings were no longer basic. The washed productwas found to show a great improvement in odor quality and was verysuitable for marketing.

Another portion of the furnace oil was treated in a like manner exceptthat the contacting was done at room temperature. The odor of theproduct was inferior to that of the product of the first treatment, butwas suitable for marketing.

Another 100 grams of poor-odor-quality furnace-oil stock was treatedunder similar conditions except the B-propiolactone was omitted. Thistreatment had little or no effect on the odor quality of the furnace-oilstock.

A similar treatment'of 100 grams of the furnace-oil stock was conductedexcept the sodium hydroxide was omitted. This treatment was withouteffect on the odor quality and the product remained unmarketable.

Example 11 A 100-gram sample of cycle stock (442-625 F. boiling range),having a very obnoxious odor and containing 0.007% mercaptan sulfur and1.01% total sulfur, was treated with two grams of 20% sodium hydroxidesolution and 0.7 gram of fl-propiolactone at 230 F. for 15 minutes withmechanical stirring. The oil and aqueous phases were then'separatedafter the mixture had cooled to room temperature. The oil waswater-washed to remove any remaining alkali. The treated oil had agreatly improved odor and was marketable.

Example 111 One hundred grams of untreated furnace oil (boiling rangesimilar to that of the furnace oil used in Example 1), containing 0.93%total sulfur and 0.046% mercaptan sulfur, and of very poor odor quality,was treated with 10 grams of 20% sodium hydroxide solution and 3.6 gramsof fi-propiolactone at 230 F. for five minutes with mechanical stirring.After the mixture had cooled to room temperature, the oil phase wasseparated and waterwashed to neutrality. The odor of the oil wassignificantly improved, but the oil was not doctor-sweet. The oil wasthen treated with an excess of doctor solution, and 0.014 gram ofsulfur, an amount just sufficient to obtain a break of the doctorsludge. The break was com plete within about two minutes. The odor ofthe doctorsweet treated oil was very satisfactory and the product wassuitable for marketing.

Another -gram sample of the furnace oil was agitated with a large excessof doctor solution while 3.6 grams of B-propiolactone were added slowly.After about three minutes, sulfur was added in small increments until abreak was obtained. Sixteen-thousandths of one gram of sulfur was addedto obtain a break in about two minutes. The product separated wasdoctor-sweet, of greatly improved odor, and marketable.

A third 100-gram sample of the furnace oil was treated with an excess ofdoctor solution and with elementary sulfur after a preliminary treatmentwith 20 grams of 20% sodium hydroxide solution for one hour at 230 F. Inthe doctor treatment, 0.025 gram of sulfur was required to obtain abreak which was not complete until after about two hours. The odor ofthe doctor-sweet product was satisfactory and it was marketable.

Example IV One hundred grams of very sour, poor-odor-quality, untreatedV.M. & P. naphtha (236289 F. boiling range), containing alkyl mercaptansmainly of primary and/or secondary types, was treated with 3.6 grams ofB-propiolactone and 10 grams of 20% sodium hydroxide solution under theconditions described in Example I. The odor of the product wasunpleasant, rendering it unmarketable as a naphtha. Another portion ofthe untreated V.M. & P. naphtha was subjected to similar treatmentexcept that fi-propiolactone Was added slowly over a 45-minute period.The odor quality of the naphtha was not improved by this treatment.

This example demonstrates that the process of this invention is noteflective in improving the odor of certain petroleum fractions. The sourV.M. & P. naphtha, which contained mercaptans mainly of primary andsecondary types, was not noticeably improved in odor when it was treatedin accordance with this invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A method of preparing a petroleum fraction of improved odor, whichcomprises treating a mercaptan-contai-ning petroleum fraction with areagent consisting essentially of a fi-lactone and an aqueous solutioncontaining an alkali metal hydroxide.

2. A method in accordance with claim 1 wherein said fi-lactone has thereactive nucleus:

hydrogen and hydrocarbon radicals containing 1 to 10 carbon atoms.

3. A method in accordance with claim 2 wherein said ,8-lactone isfi-propiolactone.

4. A method in accordance with claim 1 wherein said alkali metalhydroxide is present in said aqueous solution in an amount included inthe range of about 1 to 25% by weight.

5. A method in accordance with claim 1 wherein the treatment isconducted at a temperature of at least 150 F.

6. A method in accordance with claim 1 wherein said petroleum fractionboils within the range of approximately 300 F. to 700 F. and containstertiary mercaptans as an appreciable proportion of its mercaptancontent.

7. A method in accordance with claim 6 wherein said tertiary mercapta-nsare aromatic mercaptans of the thiophenol type.

8. In a method of preparing a doctor-sweet petroleum fraction ofimproved odor wherein a mercaptan-containing petroleum fraction istreated with doctor solution and elementary sulfur, the improvementcomprising preliminarily treating said petroleum fraction with a reagentconsisting essentially of a B-lactone and an aqueous solution containingan alkali metal hydroxide.

9. A method in accordance with claim 8 wherein said fl-lactone has thereactive nucleus:

with the free valences satisfied by the same or difierent substituentradicals selected from the group consisting of hydrogen and hydrocarbonradicals containing 1 to 10 carbon atoms.

10. A method in accordance with claim 9 wherein said fi-lactone isfl-propiolactone.

11. A method in accordance with claim 8 wherein said alkali metalhydroxide is present in said aqueous solution in an amount included inthe range of about 1 to 25% by weight.

12. A method in accordance with claim 8 wherein said preliminarytreatment is conducted at a temperature of at least 150 F.

13. A method in accordance with claim 8 wherein said petroleum fractionboils within the range of approximately 300 F. to 700 F. and containstertiary mercaptans as an appreciable proportion of its mercaptancontent.

14. A method in accordance with claim 13 wherein said tertiarymenoaptans are aromatic mercaptans of the thiophenol type.

15. In a method of preparing a doctor-sweet petroleum fraction ofimproved odor wherein a mercaptan-containing petroleum fraction istreated with a doctor solution and elementary sulfur, the improvementcomprising adding to said doctor solution a reagent consistingessentially of a B-lactone.

16. A method in accordance with claim 15 wherein said B-lactone has thereactive nucleus:

with the free valences satisfied by the same or diflerent substituentradicals selected from the group consisting of hydrogen and hydrocarbonradicals containing 1 to 10 carbon atoms.

17. A method of preparing a petroleum traction of improved odor, whichcomprises treating a mercaptancontaining petroleum fraction containingtertiary mercaptans as an appreciable proportion of its mercaptancontent with a reagent consisting essentially of a ,B-lactone having thereactive nucleus:

OO=O

with the free valances satisfied by the same or difierent sulbstituentradicals selected from the group consisting of hydrogen and hydrocarbonradicals containing 1 to 10 carbon atoms, in the presence of an aqueoussolution containing from about 1 to 25% by weight of an alkali metalhydroxide, said n-lactone and alkali metal hydroxide being used inamount at least equivalent to the tertiary mercaptan content of saidpetroleum fraction, for a period of time sufiicient to produce apetroleum fraction of improved odor.

18. In a method of preparing a doctor-sweet petroleum fraction ofimproved odor wherein a mercaptamcontaining petroleum fractioncontaining tertiary mercaptans as an appreciable proportion of itsmercaptan content is treated with doctor solution and elementary sulfur,the improvement comprising preliminary treating said petroleum fractionwith a reagent consisting essentially of a ,B-lactone having thereactive nucleus:

with the free valances satisfied by the same or diiierent substituentradicals selected from the group consisting of hydrogen and hydrocarbonradicals containing 1 to 10 carbon atoms, in the presence of an aqueoussolution containing from about 1 to 25% by weight of an alkali metalhydroxide, said S-lactone and alkali metal hydroxide being used inamounts at least equivalent to the tertiary mercaptan content of saidpetroleum fraction, for a period of time suflicient to produce apetroleum fraction of improved odor.

19. In a method of preparing a doctor-sweet petroleum fraction ofimproved odor wherein a mercaptan-containing petroleum fractioncontaining tertiary mercaptans as an appreciable proportion of itsmercaptan content is treated with a doctor solution and elementarysulfur, the improvement comprising adding to said doctor solution afi-lactone having the reactive nucleus:

with the free valances satisfied by the same or diiferent substituentradicals selected from the group consisting of hydrogen and hydrocarbonradicals containing 1 to 10 carbon atoms, said ,B-lactone being used inan amount such that the mole ratio of B-lactone to mercaptan's is notgreater than 1:1.

.20. A method in accordance with claim 16 wherein said B-lactone isfi-propiolactone.

References Cited in the file of this patent UNITED STATES PATENTS2,316,759 Bond Apr. 20, 1943 2,831,905 Nelson Apr. 22, 1958 2,946,744Ayers et a1. July 26, 1960 2,952,627 Ri ie sept- 13, 1

1. A METHOD OF PREPARING A PETROLEUM FRACTION OF IMPROVED ODOR, WHICHCOMPRISES TREATING A MERCAPTAN-CONTAINING PETROLEUM FRACTION WITH AREAGENT CONSISTING ESSENTIALLY OF A B-LACTONE AND AN AQUEOUS SOLUTIONCONTAINING AN ALKALI METAL HYDROXIDE.